Boosts then no boost then boost AHHHHHHH

Okay so ive done as much research as i can talked to 20 people had my car looked at by 4 different shops noone can figure it out. I have a 02 a4 5 speed 1.8T. Mods are Samco DV, test pipe, samco TIP, APR stage 1+ upgrade which includes injectors and software with cat delete program. I also have a Carbonio intake. When I had just stage 1 with the intake, DV and TIP the car ran fine. Since I have done the Stage 1+ and the test pipe it feels like the boost shuts off randomly. Meaning I can be driving down the road and get full boost, come to a stop light and go to take off and it is like it got put back into stock mode. It is litterally that random. I have tried changing the DV spring for a stronger one still does the same thing. Plugs and coils changed, leak test done still does the same s**t. I have no clue anymore. Any help is appreciated.

Does it boost fine then stops, and boost is back on after you restart the car?

I haven't seen that it is effected by turning the car on and off its more of a random working then not i could be on a hour drive and one minute i try to pass a car and it pulls like crazy then i pull into my lane drive 10 miles and go to pass again and its like its stock again. My mechanic is an Audi VW tech and has built alot of cars and he is stumped which doesn't happen. IDK what it could be

Quick update i fixed my random boost issue, it was a n75 valve. Didnt even have to change it, inside the n75 there was some kind of black material that came out easly. Put back the n75 and there was my boost.